Projection techniques known today can mainly be grouped in two types: Liquid Crystal Display (LCD) projectors and Digital Light Processing (DLP) projectors. The DLP projector was developed by Texas Instrument Co. The DLP technology adopts a very small mirror installed on a micro chip called a Digital Micromirror Device (DMD) to reflect light and generate highly bright and sharp projection images. Nevertheless, projectors adopting LCD or DLP usually use one single lamp as the light source to project images. To obtain higher lumens for the projector, one common approach is to use a higher power lamp. Another approach is to apply optical principles to consolidate light to achieve a greater output power so that higher lumen output is obtained to project the images.
However, lamps of a greater power usually have a shorter service life, a lower illumination efficiency and greater electric power consumption. The cost of parts also increases. Hence it is not a desirable choice.
Besides adopting lamps of a greater power, there are techniques that employ optical principles to consolidate light of lower power lamps to output light beams of a greater power. FIG. 1 illustrates one such example. It has a first paraboloids mirror 11 with a first lamp 21 located on the focus thereof and a second paraboloids mirror 12 with a second lamp 22 located on the focus thereof. According to Snell's Law, light 21A emitted from the first lamp 21 is reflected on the first paraboloids mirror 11 and projected to the second parabolids mirror 12, then is reflected to a light tunnel 40 through a rectangular prism 30. Similarly, light 22B emitted from the second lamp 22 is reflected on the first paraboloids mirror 11 and projects directly to a rectangular prism 30, which reflects the light to the light tunnel 40. Similarly, light 22A and 22B emitted from the second paraboloids mirror 12 travels in the same path to the light tunnel 40. The rectangular prism 30 allows light from the first lamp 21 and the second lamp 22 to enter the light tunnel 40 and combine the energy of the first lamp 21 and the second lamp 22.
The light consolidating system shown in FIG. 1 utilizes the feature of the paraboloids mirror and rectangular prism. The efficiency of light consolidation is between 1.3 and 1.4. There is still room for improvement in terms of energy loss of the lamps. In addition, producing the paraboloids mirrors involves a non-spherical fabrication technique, which is quite difficult. The errors of the paraboloids mirror and the rectangular prism also make output of parallel light beams difficult to achieve. As a result, the efficiency of light consolidation decreases.
Therefore, it is necessary to develop a light consolidation system that uses more than one lamp of a relatively lower power and adopts optical principles to achieve an equal amount of output lumens to increase light consolidation efficiency and remedy the problems of high power consumption and low illuminating efficiency that occur with the conventional techniques.